The boss is waiting on a number of players ahead of Saturday's Barclays Premier League visit of the Black Cats.
Sherwood refused to name the ill men but conceded he has concerns over several of his squad.
"There's a sickness bug around the training ground so there are a few players who have not been able to make training," he said.
"We have a couple of players, I don't want to tell you who who they are but they're not here today because they are ill.
"They are not well today and the doc is having to do some overtime
We could miss a couple and there's a couple who are not well now
I'd rather they weren't well now rather than tomorrow.
"There must be a bug going around, we're just hoping it's made its way to the north-east."
Sherwood could also be without Adama Traore at the weekend after the former Barcelona winger limped off in the League Cup win over Notts County on Tuesday with an ankle injury.
"He hasn't trained but we're going to give him every opportunity to be fit," said the boss.
"He's a massive talent, no-one wants him to be a sensation immediately more than I do but he has come from a weaker competition (Spain's Segunda Division, with Barca's B team) and it's going to take him time."
Sherwood played down the visit of Sunderland though, insisting no-one should read much into any early result as Villa look to avoid another season of struggle.
He said: "It's an important game but I'm not sure it's a landmark
The team got 10 points from four games last season and ended up struggling
It's not how you start, it's how you finish - and how you perform in the middle would help.
"They're under no more pressure than we are, Arsenal, Chelsea too, everyone has their own pressure
The pressure is to win football matches at whatever level.
"We want to take the game to Sunderland, they sit deep and look to bring us on and we'll certainly be coming on to them."
Source : PA
Source: PA